With progress in integration of controllers into vehicular rotating machines and miniaturization of onboard devices, semiconductor devices used for those also need reduction in size and weight and high quality.
In addition, onboard power semiconductor devices are also required dealing with high current while being reduced in size.
Therefore, power semiconductor devices using MOS-FET elements have been developed, some of which are configured such that bottom electrodes of the MOS-FET elements are soldered onto an insulation wiring substrate and their top electrodes are joined to the wiring substrate by wire bonding and then the elements are housed in a resin casing, and others are configured in such a way that the bottom electrodes of the MOS-FET elements are soldered to a metal lead frame, their top electrodes are further joined with the metal lead frame by soldering internal leads, and then those elements are resin-sealed by transfer-molding.
For example Patent documents 1 and 2 have put forward proposals on conventional semiconductor devices in which the top electrodes of MOS-FET elements are joined with a lead frame with internal leads. (See Patent documents 1, 2.)